Carburetor



J. R. EMERSON CARBURETOR Aug. 11, 1936.

Filed Feb. 5, 1931 5 Sheets-Sheet l 11mm I attomq i Aug. 11, 1936. R E R N 2,050,995

CARBURETOR Filed Feb. 3, 1931 5 Sheets-Sheet 2 Qwueflhu Monwyi 1935- J. R. EMERSON ,056,995

- CARBURETOR v I 3 Filed Feb. 3, 1931 5 Sheets-Sheet 3 gnto'u 4& s

Aug. 11, 1936. R EMERSON 2,050,995

CARBURETOR Filed Feb 5, 1931 5 Sheets-Sheet 4 r Aug. 11, 1936. J. R. EMERSON CARBURETOR Filed Feb. 3, 1951 5 Sheets-Sheet 5 Patented Aug. 11, I936 CARBURETOR John Russell Emerson, Flint,

Marvel Carburetor Company,

corporation of Illinois Mich, assignor to Flint, Mich, a

Application February 3, 1931, Serial No. 513,185 31 Claims. (Cl. 261-34) This invention relates to certain new and useful improvements in plain tube carburetors of the down draft type and more particularly to the aspirating system, the object being to provide a carburetor with an emulsion tube or nozzle having means for feeding fuel thereto from the float chamber through a constant size orifice and a variable size orifice, which supply of fuel passes through a calibrated restriction before reaching the nozzle so that both fuel supplies are metered before entering the nozzle.

Another object of my invention is to provide a novel, simple and efficient means for feeding fuel to the motor at slow and idle speeds.

A further object of the invention is to provide a system for feeding fuel for. idling which effectively eliminates the usual flat spots which occur in most carburetors at the moment the idling system goes out of service and the main nozzle system comes into service.

Another object of my invention is to provide a carburetor in which the ratio of fuel and air are fixed so as to overcome the diflicultles now existing with obtaining an accurate adjustment.

Another object of my invention is to provide a carburetor of a plain tube type which is so constructed that it can be used with advantage in a dual carburetor, the adjusting needle which controls the quantity rather than the quality of the fuel for the idling mixture being capable of controlling the mixture for idling, so that one adjustment will adjust the quantity of fuel for idling to both of the barrels of the dual carburetor.

Another object of my invention is to provide means for enrichening the mixture to aid in starting and during the warm-up period whereby an improved method of choking and enriching the mixture is produced which brings about a quick and reliable starting and warm up under all conditions.

Another object of my invention is to provide a construction of carburetor in which the vent for the float chamber is in communication .with the air cleaner so that when the cleaner becomes dirty, the increased suction under the cleaner acts on both sides of the metering orifices and prevents the fuel mixture from becoming richer.

Other and further objects and advantages of the invention will be hereinafter set forth and the novel features thereof defined by the appended claims.

In the drawings,

Figure 1 is a side elevation of a carburetor constructed in accordance with my invention, partly in section;

Figure 2 is a top plan view;

Figure 3 is a vertical section through the float chamber;

Figure 4 is a section taken on line 4-4 of Figure 2;

Figure 5 is an enlarged section taken on line 5-5 of Figure 2;

Figure 6 is an enlarged section taken on-line G-6 of Figure 2;

Figure 7 is a detail elevation showing the choke valve operated means for controlling the admission of air to the passage leading to the piston for metering the fuel;

Figure 8 is a diagrammatic view showing the various passages;

Figure 9 is an enlarged section taken on line 9-9 of Figure 1;

Figure 10 is a detail side elevation showing the application of what is known as the Johnson method of applying pressure tothe surface of the fuel in the float chamber by means of a small throttle actuated air pump; and

Figure 11 is a detail section showing the application of my improved construction of fuel feeding means to a dual type of carburetor.

In the embodiment of my invention as herein shown, I indicates the body of the carburetor which can be formed of casting or in any suitable manner, said body having a carbureting passage 2 extending therethrough in which is mounted a choke ring 3 and throttle valve 4, the portion between the throttle valve and choke ring forming the mixing chamber 5.

The throttle valve 4 is carried by a shaft 6 which is mounted in suitable'bearings formed in bosses in the body and is provided at one end with an arm 'I which is provided with a conventional type of adjustable screws adapted to engage a stop 8 for setting the throttle of the car buretor in its proper position.

The body ofthe carburetor as herein shown is provided with an integral float chamber 9 in which is mounted the float III for actuating the needle valve II for controlling'the inlet of fuel through the inlet passage l2 whereby fuel will be maintained at a predetermined level within the float chamber in the usual manner.

The float chamber is provided with a vent 9 in communication with an air cleaner A arranged above the carburetor and through which the air passes before entering the carburetor in the usual manner. By having the vent of the float chamher in communication with the air cleaner, the increased suction caused by the cleaner becoming dirty acts on both sides of the metering oriflces and prevents the fuel mixture from becoming richer.

The float chamber is provided with an ofi'set portion |3 in which is arranged a cylinder |4 having an inlet l5 at its: lower end in communication with a passage 6 which extends through the bodyof the carburetor and terminates in the carbureting passage at l1 to the engine side of the throttle valve. The cylinder I4 is surrounded by a coil spring H! which engages an arm l9 carried by a piston slidably mounted within the cylinder and adapted to be acted on by suction as will be hereinafter fully described.

The arm i9 extends laterally and is connected to the upper end of a metering pin 2| slidably mounted in a tubular member 22, the lower end of which is reduced as shown at 23 and is mounted in the upwardly extending portion of the main fuel passage 24. The tubular member is provided with oppositely disposed inlet ports 25 and a calibrated opening 26 through which the reduced end 21 of the metering pin is adapted to extend so as to meter the fuel passing from the fuel bowl into the main fuel passage 24. This main fuel passage is provided with a by-pass 28 in communication with the fuel bowl, said by-pass being calibrated so as to form a constant size outlet from the fuel bowl to the main fuel passage and in connection with the variable size fuel outlet 26, which is controlled by the metering pin, I provide a variable supply and a constant supply for the main fuel passage.

The main fuel passage 24 is provided with a calibrated restriction 29 so that the fuel passing through said fuel passage delivered through the constant supply from the bowl and the variable supply from the bowl will enters the fuel nozzle as will be hereinafter fully described.

The main fuel passage 24 terminates at its upper end in a lateral projection 30 extending into the carbureting passage 2 and has arranged therein the arm 3| of a substantially inverted V-shaped fuel nozzle 32, said nozzle being secured within the carbureting passage by a bolt 33 as clearly shown in Figure l. The other arm-34 of the nozzle 32 is arranged'c'entrally within the carbureting passage2 and terminates within the choke ring 3 at its lower end, having a deflector 35 disposed below the lower end thereof to aid in the atomizing of the fuel passage through the main arm of the nozzle 32 and to deflect it against the walls of the mixing chaniber so as to prevent the heavy particles of fuel from impinging against the throttle 4.

It will be seen that by this construction of nozzle, that the arm 34 forms an emulsion tube which is fed with fuel by the arm 3| and at the point of entrance of the arm 3| into the arm 34, I provide a deflector 36. The upper end of the emulsion tube 34 is open to the atmosphere so that air will be drawn through the emulsion tube with the fuel delivered from the main fuel passage in order to form an emulsion of fuel and an annular chamber 39 surrounding the bolt 33, I

and then into an annular chamber 39 formed by annularly reducing the arm 3| of the nozzle,'said chamber 39 being in communication with the interior of the arm 3| by a Port 40.

The body of the carburetor is provided with be metered before it.

throttle is opened further, the nozzle an idling chamber 4| open to the atmosphere through a calibrated opening 42 and has a passage 43 extending from the interior of the idling chamber 4| into the main fuel passage 24 into which is arranged the lower end of the arm 44 of a goose neck tube 45, said goose neck tube being provided with a calibrated fuel inlet 46 at one end and an air bleed opening 41 which is preferably placed at a point corresponding with the fuel level in the float chamber. but, of course, I am aware that it may be placed at any point in the goose neck tube above the fuel level without affecting the operation of the idling system.

The other leg 48 of the goose neck tube is secured in the upper end of an idling passage 49 which terminates in a chamber 50 and has ex tending therefrom a passage 5| reduced at its end and in communication as shown at 52 with the carbureting passage to the engine side of the throttle valve. A needle valve 53 is mounted in a threaded bore of the body and works through passage 55 which is reduced as shown at 56 and 30 is in communication with the carbureting passage'at a point opposite the throttle valve and is adapted to be partly closed by the throttle valve when the throttle valve is in closed position and this passage has secured therein a stand pipe 35 51 arranged within the idling chamber 4| and extending upwardly beyond the fuel level of fuel in the idling chamber as clearly shown.

Idle chamber 4| is under sub-atmospheric pressure due to the fact that vent 42 is smaller than opening 41 which is not a calibrated orifice but which leads to the suction side or motor side of the throttle through gooseneck tube 45, passages 49, chamber 50, and passages 5| and 52. In other words, air is drawn into 41 faster than itcan enter 42. When throttle blade 4 is moved, thus exposing orifice 56 tothe suction of the motor, the pressure within chamber 4| is still further reduced because of more air being drawn from 4| through standpipe 51 and passages 55 and 56, and the quantity of fuel being drawn through passage 49 is increased due to the fact that less air is bled into gooseneck 45 through opening 41.

Therefore as the throttle is opened, the pressure withinchamber 4| drops and mixture in passage 49 is enriched until the main fuel feeding system is brought into operation. As the 32 begins to feed fuel and drawing it through restricted orifices 23 and 29, thus lowers the pressure of the fuel in main passage 24 and diminishes the flow through idle fuel orifice 46.

'Extending transversely through the carbureting passage of the carburetor is a shaft 59 which carries a choke valve 59 completely closing the inlet to the carbureting passage, said choke valve being cut out to receive the nozzle 32 as shown in Figure 2, whereby the carbureting passage is completely closed when the choke valve is in closedposition so that the air passes through the f emulsion tube at a high velocity and as the fuel and air mixture enters the emulsion tube, it isv subjected to this which provides the high velocity Y stream of air, Proper mixture for starting,

One end of the shaft 58 of the choke valve is provided with a cam 60 which engages the curved end M of a rocker arm 62 pivotally mounted as shown at 63, said rocker arm having an arm 64% carrying a valve 65 which is adapted to close an air inlet 66 extending into the passage 15. This bleed hole allows passage IE to be brought into communication with the atmosphere. which breaks the suction in passage l6 and allows piston 20 to be forced upwardly by the spring 18 and to open further the orifice 26 so as to increase the supply of fuel and enrich the mixture, the construction of the operating means for this air bleed being such that normally the air bleed is closed. When starting and warming up a motor, the first portion of travel of the choke causes the valve to be withdrawn from the air bleed so that the suction is broken and the mixture is enriched as just described. As the air bleed conmunicates to the motor side of the throttle, it also supplies additional air to the motor which causes it to run faster thus preventing stalling of a cold motor with closed throttle.

Additional fuel necessary for acceleration purposes is provided by what is known as the Johnson method of applying pressure to the surface of the fuel in the float chamber by means of a small throttle actuated air pump and-in the embodiment of my invention as herein shown, an opening El is formed in the wall of the float bowl over which is arranged the outlet of a pump cylinder 68 secured to the bowl by screws 69, said pump cylinder having a piston 10 slidably mounted therein carrying a 'piston rod H which is adapted to be moved by an arm 12 carried by one end of the throttle shaft 6, it, of course, being understood that the particular manner of mounting and operating this pump to increase the pressure on the fuel in the float chamber can be varied to meet the design of carburetor and in the drawings I have only shown the same in Figure 10, as in the other figures this pump has been removed. A housing is carried by the side of the pump cylinder B8.and the pump cylinder is provided with an air outlet or by-pass 13 which is controlled by a thermostatic valve I4 which controls the amount of accelerating charge and serves as a season adjustment.

In Figure 11 I have shown adetailed sectional view of a portion of the barrels of a dual carburetor, each barrel being provided with an idling passage 5| extending from a chamber 50' and controlled by a valve 53 so that one adjustment of the idling passage adjusts the supply of fuel mixture to both carbureting passages of a dual carburetor thereby overcoming the difllculties existing in obtaining the same adjustment for'both barrels of a dual carburetor. While I have shown this particular construction, it is, of course, understood that my invention is capable of being applied to any dual carburetor of the plain tube type so that the proper mixture under all conditions will be supplied to the internal combustion engine to which the carburetor is attached.

From the foregoing description it will be apparent that I have provided a carburetor which is exceedingly simple and cheap in construction and one in which the parts are so arranged and adjusted that a very eflicient carburetor is formed and while I have shown only one embodiment of my invention, it is, of course, understood that slight changes can be made from the design of carburetor shown to produce a carburetor capable of meeting the requirements of various types of internal combustion engines to which my carbu:

retor is adapted to be attached and therefore, I do not wish to limit myself to the details of construction herein shown and described as I am aware that various departures can be made without departing from the spirit of my invention.

Prior to my invention it has been customary to provide dual means for increasing the mixture to aid in starting, such as a choke for restricting the air passage and a needle valve actuated by a movable part of the carburetor for allowing additional fuel to be fed to the mixture and I have found that in the conventional type of carburetor of this kind, the use of a .choke in most cases results in the feeding of raw fuel and almost no air to the motor and in down draft fuel feeding systems, this excess of fuel has a tendency to lead to the flooding of the motor, while with the construction of choking device for starting purposes as herein shown and described, the choke is so constructed that it surrounds the emulsion tube leaving the top of the tube open to the atmosphere. This results in the entire suction force of a motor being exerted on the emulsion tube, thereby resulting in a highly atomized mixture of fuel and air being fed to the motor, as fuel and air is fed to the motor rather than raw fuel whereby a highly combustible mixture is obtained, which aids in the ready starting of the motor.

It will also be seen that I have provided means for enriching the mixture for starting and warming up by a vacuum step-up system and in connection with the means for breaking the vacuum in this system when the choke valve is moved into closed position and I feed air into the carbureting passage to the engine side of the carburetor thus speeding up the idle and preventing stalling of a cold motor.

In the operation of an internal combustion en glne to which my improved construction of carburetor is adapted to be attached, the gasoline is fed to an emulsion tube from a conventional float chamber and the fuel is fed from the float cham her by means of a constant size orifice and a variable size orifice which is controlled by a metering pin actuated by a vacuum step-up enriching means comprising a metering pin actuated by a piston in a cylinder within the float chamber, which cylinder is in communication with the carbureting passage of the charge forming device beyond the throttle valve so that when the throttle valve is closed or nearly so, the suction in this passage leading to the cylinder is sufficiently strong to overcome the spring so as to cause the piston to travel downwardly which forces the metering pin into the orifice 26, thereby restricting the amount of fuel fed into the mainfuel passage 24. As the throttle is open, the suction or' vacuum beyond the throttle decreases, which enables the spring to force the piston upwardly, thereby raising the metering pin and allowing an increased amount of fuel to flow through the oriflce 26 and in this way it is possible to vary the quality of the mixture automatically in order to meet the various demands of the motor to which the carburetor is attached.

In the construction herein shown, air is bled into the arm 3! of the nozzle through air passage 31, annulus 38 and port 40 and as the fuel and air mixture enters the emulsion tube, it is subjected to a high velocity stream of air entering the emulsion tube at its upper end. The fuel and air or emulsion is picked up by this high velocity of air and drawn downwardly and is brought into engagement with the deflector arranged below the emulsion tube, which serves choke ring being disposed at the lower end of the emulsion tube in place of the conventional venturi to form means for restricting the mixture passage at the point of discharge of the emulsion nozzle.

In the operation of the carburetor for feeding fuel mixture at slow and idling. speed, air is allowed to enter the idling chamber 4i through the air inlet 42 and air is bled into the tube 45 through the opening 41 which is here shown at a point above the fuel level in the float chamber.

In the construction shown, the vent 42 open to the atmosphere is smaller than the opening 41 and as this opening communicates with the suction side of the'throttle, air will be drawn from chamber 4| faster than it can enter through vent 42, giving a condition of sub-atmospheric pressure in chamber 4|. As passage 55 through which only air passes leads from the idling chamber 4| to a point opposite the edge of the throttle in the carbureting passage, as the throttle is open, the passage 55 becomes subject to the suction of the motor, placing chamber 41 under a still stronger sub-atmospheric pressure and this in turn enables the passage 49 to feed more fuel to the motor until a point is reached where the main aspirating system cuts in. It is stated at this point that the passage 55 under no. condition feeds carbureted air or any fuel as this passage is solely an air passage. The suction through the emulsion tube or nozzle 34 is so strong that when it comes into service, it will withdraw the fuel in passage 48 to a point below opening 41, thereby cutting out of service the idling system. However, as soon as suction through the main aspirating system becomes weaker than the subatmospheric'pressure in chamber 4|, the idling system will come into service to supply the motor whereby I am able to obtain an effective idling system, which effectively eliminates the usual flat spots which occur in most carburetors at the moment the idling system goes out of service and the main fuel nozzle comes into service.

In the conventional type of carburetor, the idle adjustment varies either the proportion of air or that of fuel in the idling mixture, which makes it necessary to provide two idle adjustments of the conventional dual carburetor with the difficulty of getting the same adjustment for both carbureting passages of the dual carburetor and I have found that with the construction as herein shown and described, the air and fuel ratio are fixed which provides novel means for obviating this difilculty and enables me to obtain an accurate adjustment.

When this construction of carburetor is used in the dual carburetor, the passage 5| can be split for the reason that this passage adjusts only the quantity of the mixture fed to the motor and not the quality, whereby I obtain a very simple and accurate means of idle adjustment for dual carburetors which is not affected by the adjustment by unskilled persons.

With the use of a fuel enriching means of the type known as the vacuum step-up and with the accelerating system known as the- Johnson method of applying pressure to the surface of the fuel in the float chamber for acceleration, I provide a carburetor which embodies certain bustion engines having a carbureting passageprovided with a choke ring disposed therein, a downwardly extending emulsion tube disposed within said carbureting passage having its lower end terminating within said choke ring, a deflector carried by the lower end of said emulsion tube, a fuel passage for said emulsion tube, constant and variable fuel feeding means for said fuel passage and means for bleeding air into said fuel passage.

2. A carburetor having a carbureting passage provided with an emulsion tube, a fuel passage for said tube, an idling chamber having a vent opening, a goose neck tube disposed in said idling chamber in communication with said fuel passage, an idling passage extending from said goose neck to said carbureting passage beyond the throttle valve and an air passage extending from said carbureting passage to said idling chamber through which only air passes adapted to be partly closed by the throttle when in closed position.

3. A carburetor having a carbureting passage provided with a choke valve at one end and a throttle valve, an emulsion tube disposed under said choke valve, a fuel passage for feeding fuel to said emulsion tube, variable and constant fuel feeding means for said fuel passage, vacuum actuated means for controlling said variable fuel feeding means and means actuated by said choke valve for rendering said vacuum actuated means inoperative when said choke valve is moved into rendering said variable fuel feeding means inoperative.

5. A carburetor comprising a body having a emulsion tube disposed within said carbureting passage, a fuel passage for feeding fuel to said emulsion tube, a series of fuel feeding passages fromsaid fuel bowl to said fuel passage, a metering pin disposed in one of said fuel feeding passages, a cylinder disposed in said fuel bowl, a piston dis posed in said cylinder having a connection with said metering pin, a spring for normally holding said piston in raised position, a passage extending from said carbureting passage to said cylinder,

carbureting passage and a float chamber, an

and means for venting said last mentioned pas- 70 sage.

6. A carburetor having a carbureting passage and a fuel bowl, an emulsion tube disposed in said carbureting passage, a throttle valve disposed in said carbureting passage, constant and variable means for feeding fuel from said fuel bowl to said emulsion tube, an idling chamber having an air vent, a passage leading from the idling chamber to said carbureting passage through which only air is adapted to pass, said passage being partly closed by the throttle valve, a goose neck disposed in said idling chamber in communication with the fuel feeding means, a vent in said goose neck and a passage leading from one of the arms of said goose neck terminating in said carbureting passage to the engine side of said throttle valve.

7. A carburetor having a carbureting passage provided with a throttle valve, a centrally disposed downwardly extending emulsion tube arranged within said carbureting passage, a choke valve surrounding said emulsion tube, a main fuel passage, a float chamber for supplying fuel to said fuel passage, a vacuum actuated piston for controlling the passage of fuel from said float chamber to said fuel passage, a passage extending from said carbureting passage to said vacuum actuated piston, an air vent for said last mentioned passage and a valve for closing and opening said air vent actuated by said choke valve.

8. A carburetor having a float chamber and an idling chamber, a carbureting passage providedwith an emulsion tube and a throttle valve, a main fuel passage extending from said float chamber to said emulsion tube, a restriction in said main fuel passage, a goose neck disposed within said idling chamber in communication with said main fuel passage, a vent for said goose neck, a vent for said idling chamber, and a passage extending from the upper end of said idling chamber to said carbureting passage and through which air only is adapted to be drawn by the suction of the engine, said passage being adapted to be partly closed by the throttle valve, an idling passage extending from said goose neck to said carbureting passage to the engine side of the throttle valve and a valve for controlling the quantity of fuel mixture passing through said idling passage.

9. A down draft carburetor for internal combustion engines having a carbureting passage open to the atmosphere at its upper end and adapted to be connected to an intake manifold at its lower end, a centrally disposed emulsion tube disposed in the upper end of said carbureting passage having a deflector disposed below the lower end thereof, a choke ring surrounding said tube at its lower end within said carbureting passage, a fuel bowl, constant and variable means for feeding fuel from said fuel bowl to said emulsion tube, means for bleeding air into said emulsion tube and a choke valve surrounding said emulsion tube at its upper end.

10. A carburetor of the down draft type comprising a body having a carbureting passage extending therethrough, said carbureting passage being provided with an offset, an inverted V- shaped nozzle having one of its legs arranged within said offset and the other leg disposed centrally within said carbureting passage, a fuel bowl, constant and variable means for feeding fuel from said fuel bowl to said emulsion tube and means for bleeding air to one of the legs of said nozzle.

11. A carburetor comprising a body having a carbureting passage extending therethrough and provided with an idling chamber and a fuel bowl, an emulsion tube disposed within said carbureting passage, a throttle valve disposed in said carbureting passage, a fuel passage extending from saidfuel bowl to said emulsion tube, an idling passage extending from said idling chamber to said carbureting passage, said idling passage being provided with a goose neck in communication with said fuel passage, said goose neck being provided with a vent, a vent for said idling chamber, a passage extending from said idling chamber 'to said carbureting passage and terminating at the lip of said throttle valve when in closed position and through which air only is adapted to pass and vacuum controlled means for controlling the supply of fuel from said fuel bowl to said fuel passage.

12. A carburetor comprising a body having a carbureting passage extending therethrough and provided with an idling chamber and a fuel bowl,

an emulsion tube disposed within said carbureting passage, a throttle valve disposed in said passage, a fuel passage extending from said fuel bowl to said emulsion tube, an idling passage extending from said idling chamber to said carbureting passage, said idling passage being provided with a goose neck in communication with said fuel passage, said goose neck being provided with a vent, a vent for said idling chamber, a passage extending from said idling chamber to said carbureting passage and terminating at the lip of said throttle valve when in closed position and through which air only is adapted to pass, vacuum controlled means for controlling the supply of fuel from said fuel bowl to said fuel passage, a choke valve in said carbureting passage and means actuated by said choke valve for rendering said vacuum controlled means inoperative.

13. A down draft carburetor for internal combustion engines having a carbureting passage provided with a downwardly extending open ended emulsion tube, a nozzle for feeding fuel into said emulsion tube, means for bleeding air into said nozzle and a pivoted choke valve surrounding said emulsion tube, the open end of said emulsion tube and the air feeding means for said nozzle being open to the atmosphere.

14. A down draft carburetor for internal combustion engines having a carbureting passage with a centrally disposed downwardly extending emulsion tube having open ends and of substantially the same diameter throughout its length and through which air passes in its passage through the carbureting passage, a main fuel passage for delivering fuel into-said emulsion tube, a float chamber, constant and variable means for feeding fuel from said float chamber to said fuel passage and vacuum actuated means for controlling said variable fuel feeding means.

15. A down draft carburetor for internal combustion engines having a carbureting passage with a centrally disposed downwardly extending emulsion tube through which air passes in its passage through the carbureting passage, a deflector disposed beyond the discharge of said emulsion tube, a main fuel passage for said emulsion tube, an air bleed for said fuel passage, a float chamber, constant and variable means for feeding fuel from said float chamber to said fuel passage and vacuum actuated means for controlling said variable fuel feeding means.

16. A down draft carburetor for internal combustion engines having a carbureting passage with a centrally disposed downwardly extending emulsion tube, said emulsion tube being provided with open ends and through which a portion of the air passes in its passage through the carbureting passage, a main fuel passage for said tube, a, choke valve for said carbureting passage, a float chamber, constant and variable means for feedspreader disposed below the discharge end of said emulsion tube, a fuel passage for said emulsion tube, a float chamber, a series of fuel outlets from said float chamber to said fuel passage, a metering pin for one of said fuel outlets and vacuum actuated means for operating said metering pin.

18. A down draft carburetor for internal combustion engines comprising a carbureting passage, an emulsion tube disposed in said carbureting passage having open ends and through which a portion of the air passes in its passage through said carbureting passage, a fuel passage for feeding fuel to said emulsion tube, a choke valve for said carbureting passage, means controlled by the vacuum existing in the carbureting passage for controlling the supply of fuel to said fuel passage and means actuated by said choke valve for rendering said controlling means.

inoperative.

19. A carburetor comprising a carbureting passage having a throttle valve, a choke valve disposed therein, a fuel bowl, an idling chamber, an emulsion tube disposed axially within said carbureting passage provided with ends open to the carbureting passage and; of substantially the same size throughout its length, constant and variable fuel feeding means for said emulsion tube, said variable fuel feeding means being controlled by vacuum actuated means, said idling chamber being in communication with said fuel feeding means, a passage extending from said idling chamber to said carbureting passage to the engine side of the throttle valve and a valve controlling the quantity of fuel mixture passing therethrough.

20. A carburetor having a carbureting passage with a throttle valve disposed therein, a downwardly extending emulsion tube disposed in said passage having open ends and through which air is adapted to pass in its passage through the carbureting passage, a fuel bowl, a fuel passage extending from said fuel bowl to said emulsion tube, a metering pin for controlling the passage of fuel from said fuel bowl to said fuel passage, a piston for actuating said metering pin and means controlled by the vacuum existing in the carbureting passage to the engine side of the throttle valve for actuating said piston.

21. A carburetor having a carbureting passage with means for feeding an emulsion of fuel and air thereto including adownwardly extending emulsion tube through which a portion of the air in its passage through the carbureting passage passes, vacuum actuated means forregulating the volume of fuel fed to said emulsion tube, a choke valve and means actuated by the choke valve for rendering said vacuum actuated means inoperative.

22. A carburetor comprising a body having a carbureting passage extending therethrough provided with a throttle valve, a float bowl, an emulsion tube-disposed in said carbureting passage, a fuel passage extending from said fuel bowl to said emulsion tube, means actuated by the vacuum existing in the carbureting passage, for metering the fuel passing from said fuel bowl,

an idling chamber in communication with said fuel passage and provided with a vent, an idling passage extending from said idling chamber to said carbureting passage, and means for producing sub-atmospheric pressure within said idling chamber comprising a passage extending from said idling chamber to said carbureting passage and through which air only passes.

23. A down draft carburetor having a carbureting passage, an emulsion tube disposed therein provided with open ends, means for feeding fuel to said emulsion tube in which is formed a combustible mixture of fuel and air and adeflector carried by the lower end of said emulsion tube and disposed below the discharge end of said emulsion tube for spreading the emulsion delivered from said tube.

24. A down draft carburetor having a carbureting passage provided with a valve controlled inlet and a valve controlled outlet, an emulsion tube disposed in said carbureting pas sage having open ends and through which air passes in its passage through the carbureting passage, means for feeding fuel to'said emulsion tube in which is formed a combustible mixture of fuel and air and a deflector carried by said emulsion tube and disposed below the discharge end of said emulsion tube for spreading the enmision delivered therefrom.

25. A carburetor comprising a carbureting passage having a throttle valve, a fuel bowl, an idling chamber, an emulsion tube disposed with: in said carbureting passage provided with an inlet end open to the carbureting passage to allow a portion of the air passing through said carbureting passage to pass through said tube, constant and variable fuel feeding means for said emulsion tube, said variable fuel feeding means being controlled by vacuum actuated means, said idling chamber being in communication with said fuel feeding means, and an air only passage extending from said idling chamber to said carbureting passage to the engine side of the throttle valve.

26. A carburetor having a carbureting passage Q provided with a throttle valve, a centrally disposed downwardly extending emulsion tube arranged within said carbureting passage, as main fuel passage, a float chamber for supplying fuel to said fuel passage, a vacuum actuated piston for controlling the passage of fuel from said float chamber to said fuel passage, an air passage extending from said carbureting passage to said vacuum actuated piston for subjecting the piston to the vacuum therein, and means for venting said airpassage to break the vacuum on the piston.

27. A down draft carburetor for internal combustion engines having a carbureting passage provided with a throttle valve, a choke ring disposed within said carbureting passage, a downwardly extending emulsion tube disposed within said carbureting passage having its lower endterminating within said choke ring, a deflector disposed in alignment with said emulsion tube below the choke ring, a fuel pasage for said emulsion tube, and constant and variable fuel feeding means for said fuel passage.

28. A carburetor comprising a body having a carbureting passage extending therethrough and 70 bowl, an idling passage in communication with u said fuel passage and discharging into said carbureting passage beyond the throttle valve, said idling passage having a vent opening to said idling chamber, and an air passage through which air only passes extending from said idling chamber to said carbureting passage, said air passage terminating at a point in the carbureting passage so as to be partly closed by the throttl valve when in closed position.

29. A carburetor comprising a body having a carbureting passage extending therethrough and an idling chamber and a fuel bowl, a throttle valve controlling said carbureting passage, a jet discharging into said carbureting passage, 8. fuel passage for said jet drawing fuel from said fuel bowl, an idling passage in communication with said fuel passage and discharging into said carbureting passage beyond the throttle valve, said idling passage having a vent opening to said idling chamber, an air passage through which air only passes extending from said idling chamber to said carbureting passage vacuum controlled means for varying the supply of fuel from said fuel bowl to said fuel passage, a choke valve in trolling the flow of fuel from said fuel bowl to said jet, vacuum actuated means for controlling said feeding means comprising a piston and cylinder, a spring urging said piston in a direction to increase the flow of fuel permitted by said feeding means, and a passage extending from said piston and cylinder to said carbureting passage to communicate the depression in said carbureting passage to the cylinder whereby the piston is urged to decrease the flow of fuel, an air 10 vent for said passage, and a valve controlling said vent actuated by said choke valve.

31. A downdraft carburetor for internal combustion engines having, in combination, a carbureting passage, a centrally disposed downwardly discharging emulsion tube in said passage having open ends both in unrestricted communication with the passage and through which air passes in its passage through the carbureting passage, a throttle on the discharge side of said emulsion tube, a. main fuel passage for delivering fuel into said emulsion tube, a fuel supply chamber, a fuel port connecting said fuel supply chamber and said fuel passage, a second constantly partially open fuel port connecting said fuel supply chamber and said passage, :1 metering pin for controlling the flow of fuel through said second port, and means responsive to the vacuum in said carbureting passage for controlling said metering pin. 3

JOHN RUSSELL EMERSON. 

